Nonaqueous Electrode Binder Distribution for Battery Cycle Life
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face a trade-off between high capacity and long life through large-current cycles, as increasing electrode density to enhance capacity often compromises cycle life due to reduced lithium ion diffusion paths.
Innovation Solution
A negative electrode configuration with a rubber polymer binder (A) predominantly in the collector-side region and a water-soluble polymer binder (B) around the active material, optimizing the distribution of the negative electrode active material and binders to facilitate uniform SEI coating and maintain lithium ion diffusion paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the density of the electrode is increased to achieve high capacity, then the battery capacity is improved, but the diffusion paths of lithium ions are reduced, resulting in poor cycle life through large-current cycles
Solution Approach 1:
The patent applies local quality by creating distinct regions within the negative electrode mix layer: a collector-side region with higher binder A content and different active material perimeter distribution, and a surface-side region with different characteristics. This spatial differentiation allows the electrode to simultaneously achieve high density for capacity while maintaining sufficient lithium ion diffusion paths for cycle life, as each region performs its specific function optimally.
2Duration of action of moving object
If the adhesion between the mix layer and collector is strengthened to achieve long cycle life, then the cycle life is improved, but the amount of binder must be increased, which may sacrifice battery capacity
Solution Approach 1:
The patent uses local quality by concentrating binder A (rubber polymer compound) specifically in the collector-side region where strong adhesion is needed for cycle life, while the surface-side region has different composition. This localized binder distribution achieves the required adhesion strength for long cycle life without uniformly increasing binder content throughout the electrode, thereby preserving battery capacity.
Solution Approach 2:
The patent employs composite materials by combining two different binder types: binder A (rubber polymer compound) for strong adhesion to the collector, and binder B (water-soluble polymer compound) for binding active material particles. This composite binder system achieves both strong adhesion for cycle life and minimal capacity loss, as each binder component performs its specific function efficiently.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves high capacity and extended cycle life by ensuring uniform SEI coating and suppressing lithium ion deactivation, even under large-current charge and discharge conditions.
Implementation Method 1
the adhesion between a mix layer and collector of an electrode and the adhesion of an active material in the mix layer are preferably strong
Implementation Method 2
diffusion paths of lithium ions are reduced
Data Source
AI summary
A nonaqueous electrolyte secondary battery comprising a negative electrode plate including a negative electrode collector and a negative electrode mix layer which is placed on the negative electrode collector and which contains a negative electrode active material, a binder A containing a rubber polymer compound as a binder, and a binder B containing a water-soluble polymer compound. The negative electrode mix layer has a cross section in a thickness direction thereof, the cross section being halved into a collector-side region and a surface-side region. The sum of the perimeters of the negative electrode active material per unit area in the cross section is more distributed in the collector-side region than in the surface-side region. The binder A is more distributed in the collector-side region than in the surface-side region.